Surgical cables and wires are used extensively in orthopedic surgery for securing bones and bone fragments in place and for fastening surgical implants to bones. In the most common type of orthopedic surgery where severe breaks of bones have taken place, or in reconstructive procedures on bones, for example in reconstructive hip procedures or the like, a permanent cable implant is provided to hold bone portions together. For example, during a total hip replacement, press-fit femoral components are inserted into the canal of the femur, resulting in an extremely tight fit in some cases. Seating of these press-fit components has been shown to induce large hoop stresses in the proximal femur, which can result in longitudinal cracks in the femur. Thus, a surgical cable system is applied for providing a counteracting compressive hoop stress, which prevents crack formation and/or propagation.
Typically, surgical cables are implanted using tensioning devices, which apply tension to a cable looped around the bone and the cable implant. The cables are typically formed into a loop, simple or complex, and tightened about the bone structure and implant with a tensioning tool.
These tensioning tools are often cumbersome due to the strength required to support the device while creating high tensile forces in the surgical cables. Cable tensioning tools are also extremely slow to operate because of threaded drives used to create the large tensile forces in the surgical cable. The slow operation of cable tensioners can cause significant delays in the surgery itself. Any delays in surgery prolong the time required for the patient to be under general anesthetic increasing the risk of complications and recovery time of the patient.
Finally, many cable tensioning tools are long and narrow in which cable is thread blindly through the device. These cable tensioning tools are extremely complicated and difficult to operate under the stress and time constraint of surgery especially during trauma cases. Furthermore, complicated mechanisms have an increased likelihood of mechanical malfunctioning, i.e. jamming, and the restoration of function is extremely difficult due to the blind threading of cable in the devices.
One example is shown in U.S. Pat. No. 5,312,410 filed Dec. 7, 1992 to Miller et al. In the Miller example, a rudimentary ratchet mechanism is used to create cable tension thread blindly through the device. The ratchet mechanism causes force to be transmitted from a lever directly to the ratchet teeth of the device causing shock waves from the intermittent motion and imprecise positioning of tensioned cable due to mechanical backlash. The imprecise positioning of the device can cause imprecise tensioning in the attached cable and could further damage the patient's fragile bones.
Another example is shown in U.S. Patent Application Pub. No. US 2006/0229623 A1 filed Feb. 21, 2006 to Bonutti et al. In the Bonutti example, the pistol grip is used only to crimp the cable and the proximal lever is used to actually tension the cable. The Bonutti example requires wrapping the cable around a cylinder by hand and awkwardly rotating the lever to achieve a small amount of cable being drawn through the instrument. Such awkward operation of medical instruments is not intuitive to medical personnel unfamiliar with complicated mechanical systems.